primitive Functional, couldn't find 'add' in 'None'

[jkleiser]

Hi, and thanks a lot for a great presentation!

I'm still very much a Pony beginner. I got curious re. your "primitive Functional" at my-little-pony.html#/7/4, and just pasted your 4 lines into an existing fibo.pony file I had. When trying to compile, I got things like this:

fibonacci/fibo.pony:7:38: couldn't find 'add' in 'None'
  fun fib(n: U64): U64 => fib(n - 1) + fib(n - 2)
                                     ^

Is there some way to supply the missing 'add', or was this just some "fantasy" example?

[darach]

Hi Jon,

Strange. Could it be something to do with overloading infix ops if you have an 'add' function? Happy to look at the fibo.pony file - maybe there's a bug here that needs squashing somewhere...

Cheers,

Darach.

[jkleiser]

Here's my fibo.pony:

use "time"

// https://cdn.rawgit.com/darach/my_little_pony/master/my-little-pony.html#/7/4

primitive Functional
  fun fib(0): U64 => 0
  fun fib(1): U64 => 1
  fun fib(n: U64): U64 => fib(n - 1) + fib(n - 2)       // couldn't find 'add' in 'None'

actor Main
  let _env: Env

  new create(env: Env) =>
    _env = env
    try
      let n = _env.args(1).u8()
      _env.out.write("Fibonacci(" + n.string() + ") = ")
      Time.perf_begin()
      let start = Time.micros()
      let fib = fibonacci(n)
      let stop = Time.micros()
      Time.perf_end()
      _env.out.print(fib.string())
      _env.out.print("Time used: " + (stop - start).string() + " micros")
    else
      _env.err.print("An error occurred in Main.create")
      _env.exitcode(-1)
    end

  fun fibonacci(n: U8): U64 =>
    if n <= 2 then
      1
    else
      fibonacci(n - 1) + fibonacci(n - 2)
    end

[darach]

Hi Jon,

This is from the 'promises' section of the talk which is about planned features! The good news is, you can track progress here for the functional programming style function overloading which is what you are trying to use:

https://github.com/CausalityLtd/ponyc/issues/351

Some of the planned features such as C-like structures are already available on master.

Cheers,

Darach.

[jkleiser]

Yes, good news. Thanks!